1. Field of the Invention
The present invention is directed toward manufacturing and assembly techniques and, more particularly, toward an automated method for tensioning an automobile power steering belt.
2. Description of Related Art
During assembly of automobile engines, it is necessary to install various accessory devices on the engine and to connect at least some of these accessory devices to rotary power from the engine. For example, the air conditioning compressor and the power steering pump must be mounted adjacent the engine and connected, via pulleys and belts, to the engine crank shaft pulley.
Conventionally, an adjustable mount is provided to permit the pump to be moved relative to the crank shaft pulley to vary the tension on the belt. As such, this portion of the manufacturing process is manual, and depends greatly upon the skill of the assembler. If the tension on the belt is not enough (i.e., belt too slack), the belt may slip. If the tension on the belt is too great (i.e., belt too tight), the belt may wear prematurely. Accordingly, setting the belt to the proper tension has largely been based upon the xe2x80x9cfeelxe2x80x9d of the assembler, which is the result of experience and individual perceptions that is difficult, if not impossible, to standardize among different assemblers. Moreover, switching of belt materials, which may require relatively more or less tension, is problematic due to the tendency of assemblers to continue to set the belt tension in the manner in which they are accustomed.
Therefore, there exists a need in the art for a method and device to automate setting of the belt tension.
The present invention is directed toward a method and apparatus to automate and standardize the setting of tension on a belt.
In accordance with the invention, a belt tensioning apparatus is provided as a station on the automobile assembly line. Palletized engines are directed to the belt tensioning station and are released from the station after having their belt(s) appropriately tensioned.
In accordance with a method of the present invention, a vibration sensor is placed adjacent the belt and a tensioning device, which is operable to increase tension on the belt, is activated. The belt is thereafter struck to cause the belt to vibrate. The belt vibrations are measured with the vibration sensor and a frequency of the measured belt vibrations is compared with a predetermined desired vibration frequency. If the measured vibration frequency is below the predetermined desired vibration frequency, the belt tensioning, striking and vibration measuring continues. When the measured vibration frequency is equal to or greater than the predetermined desired vibration frequency, the tensioning device is deactivated. The predetermined desired vibration frequency corresponds to a predetermined belt tension.
In further accordance with the method of the present invention, following deactivation of the tensioning device, a final belt tension check is performed wherein the belt is struck at least one further time to cause the belt to further vibrate. The further vibrations are measured by the vibration sensor and a frequency of the further belt vibrations are compared to a predetermined range of belt vibration frequencies. If the further belt vibration frequency is within the predetermined range of desired belt vibrations, the belt tension is determined to be acceptable.
In accordance with a belt tensioning system of the present invention, a belt striker, vibration sensor, tension controller, and tensioning device are provided. The tension controller is operable to activate the belt striker and to receive measured belt vibration signals from the vibration sensor. The tension controller compares a frequency of the measured belt vibrations with a predetermined desired belt vibration frequency. The tension controller is also operable to activate and deactivate the belt tensioning device in response to measured vibration frequency. When the measured vibration frequency is below the predetermined desired belt vibration frequency, the tensioning device is activated to increase tension on the belt and, when the measured vibration frequency is equal to or greater than the predetermined desired vibration frequency, the tensioning device is deactivated by the tension controller.
In further accordance with the present invention, the belt striker and vibration sensor are carried on a tension measuring head. The tension measuring head also includes a proximity sensor that is in communication with the tension controller and operable to indicate to the tension controller when the tension measuring head is properly positioned relative to the belt to be tensioned.
In further accordance with the present invention, the tensioning device is an air driven gun, and the system further includes a solenoid air control valve. The tension controller is operable to open the solenoid air control valve to activate the air driven gun and to close the solenoid air control valve to deactivate the air driven gun.